package java190904;

import java.util.Scanner;

public class Test19092301 {
	public static void main(String[] args) {
		Scanner Scanner = new Scanner(System.in);
		int F =Scanner.nextInt();
		float C;
		C=(F-32)*5/9;
		System.out.printf("%.4f",C);
		Scanner.close();

	}
	}